Method of manufacturing rods or wire of compound material

ABSTRACT

In manufacturing a rod or wire of compound material from a core of aluminum or aluminum alloy and a casing of copper or copper alloy by hydrostatic extrusion, a billet is used in which the core has a smaller external diameter than the internal diameter of the casing, so as to provide clearance therebetween sufficient that at least most damage to the casing during soft-annealing and handling will not be of sufficient extent to prevent the insertion of the core into a casing. An internal space is provided at the rear of the billet to collect the air present in the gap between the core and the casing as it is displaced when the core and casing are pressed into contact with each other.

United States Patent Nilsson et a1.

[ 1 Dec. 11, 1973 METHOD OF MANUFACTURING RODS OR WIRE OF COMPOUNDMATERIAL Inventors: Jan Nilsson, Robertsfors; Bertram Brinkeborn,Vasteras, both of Sweden Allmanna Svenska Elektriska Aktiebolaget,Vasteras, Sweden Filed: Feb. 16, 1972 Appl. No.: 226,759

Assignee:

Foreign Application Priority Data Mar. 4, I971 Sweden ..2756 /71 US. Cl29/474.3, 29/479, 72/60 Int. Cl B2ld 39/04 Field of Search 72/60;29/4733,

References Cited UNITED STATES PATENTS 3,698,067 10/1972 Feiss..29/474.3X

Primary Examiner-J. Spencer Overholser Assistant Examiner-RichardBernard Lazarus Attorneylennings Bailey, Jr.

[57] I ABSTRACT In manufacturing a rod or wire of compound material froma core of aluminum or aluminum alloy and a casing of copper or copperalloy by hydrostatic extrusion, a billet is used in which the core has asmaller external diameter than the internal diameter of the casing, soas to provide clearance therebetween sufficient that at least mostdamage to the casing during soft-annealing and handling will not be ofsufficient extent to prevent the insertion of the core into a casing. Aninternal space is provided at the rear of the billet to collect the airpresent in the gap between the core and the casing as it is displacedwhen the core and easing are pressed into contact with each other.

8 Claims, 2 Drawing Figures BACKGROUND OF THE INVENTION 1. Field of theInvention The present invention relates to a method of manufacturingrods or wire of compound material having a core of aluminum or analuminum alloy and a casing of copper or a copper alloy surrounding thecore, by means of hydrostatic extrusion. At the start of themtrusion acompound billet is used consisting of a core of aluminum andasurrounding casing of a copper tube which are inserted in a pressurechamber containing a pressure medium. Under the influence of a highallsided hydrostatic pressure, the billet is forced out through anopening in a die and thus shaped to a product with the desiredcross-section. During this process the core and casing at the rear endof the billet are tightly sealed, for example with a sealing ring or alid of elastomeric material which prevents pressure medium frompenetrating between the core and the surrounding tube.

2. The Prior Art The prior applications of Burstrom, Ser. No. 32,195,filed Apr. 27, 1970 now U. S. Pat. No. 3,654,687 and Nilsson, Ser. No.758,308, filed Sept. 9, 1968 now U. S. Pat. No. 3,620,059 describehydrostatic extrusion of compound products having a core of one materialand a casing of another material.

It has been found that there are practical difficulties in joining acore and a casing if the clearance between them is small. Duringsoft-annealing and handling of the tube for the casing it may curve,become ovalor be subjected to knocks resulting in dents. It may then bedifficult or indeed impossible to insert the core in the casing.

SUMMARY OF TI-IE INVENTION The difficulties of insertion can beeliminated by making the clearance between the'core and the casing solarge that normal'alterations in shape during annealing and handling ofthe copper tubing are of no importance; The considerable volume of airwhich is enclosed between the core and the casing'if there is muchclearance may cause difficulties during the extrusion. Air bubblesenclosed between the core and the casing may jeopardize the adhesion andthe casing may be loosened from the core in the finished product.According to the invention, the risks of the faults described above areeliminated by shaping the billet so that the quantity of air enclosed iswith all certainty collected at the rear end of the billet which remainsafter the extrusion is complete. This can be achieved by arranging aspace to collect the air at the rear end of the billet, the. surroundingwalls have such strength that material in the copper casing or aluminumcore is only pressed into this after the casing, under influence of thepressure in the surrounding pressure medium, has been pressed intocontact with the core to such an extent that the gap between casing andcore is disappeared.

Suitably an annular air-collecting space is arranged between the coreand the casing at the rear part of the billet. If a pressure plate ofsteel, for example, is used, the annular space can be effected bybevelling the plate or a space can be arranged in the pressure plate andit may be shaped with grooves or channels through which air. can flowinto the space.

It may be desirable to provide the core or copper tube with an axialgroove through which air can flow back to the air-collecting space ifthe tube should be first pressed into contact with the core at the rearend of the billet upon a pressure increase in the pressure chamber. Theinvention makes it possible to have considerable clearance between thecore and the casing without any risk that the enclosed air volume willcause any disturbance during the compression or that air pockets willexist in the finished product.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is further describedwith reference to the accompanying drawings. FIG. 1 shows schematicallya section through a pressure chamber with a billet inserted and FIG. 2shows on a larger scale the rear end of a billet with an alternativedesign of an air-collecting space.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the drawings, 1 designates apress stand and 2 a pressure-generating piston which is arranged in anhydraulic pressure device, not otherwise shown, in which there is acylinder to operate the piston 2. The pressure chamber comprises a highpressure cylinder 3 which is constructed of a steel cylinder 4, a stripsheath 5 of rectangular tape of high strength wound on under prestress,and end pieces 6. Between the end closures6 and a spacing sleeve 7 inthe cylinder are two seals 8 and 9 sealing between the cylinder 4 andthe extrusion die 10 and piston 2, respectively. In the pressure chamberis a billet 11 consisting of a core 12 of aluminum or an allumiunm alloyand a surrounding casing 13 of copper or a copper alloy. Between thecore 12 and the casing 13 there is considerable clearance so that anannular gap 14 is formed. The radial clearance for a core having adiameter of mm may be 5 mm or more. The clearance is usually between Iand 5 mm. A steel plate 15 is inserted at the rear end of the billet. Alidshaped seal of elastomeric material surrounds the rear end of thebillet and covers the joint between the plate 15 and the casing 13 andthus prevents the surrounding pressure medium 17 from penetrating intothe gap 14. The plate 15 has a section "18 which projects into the tube13. The projection 18 has a triangular bevelling 19.

In the embodiment shown in FIG. 1, the tube 13 is supported by theprojection 18. The tube 13 thus acquires a certain support so that itwill be pressed against the billet 12 before the tube material ispressed into the triangular air-collecting space 20 formed by the tube13, the triangular bevelling l9 and the end surface of the core 12. Toensure that the air will collect in the space 20 even if the tube 13should be pressed against the core 12 at the rear of the billet beforebeing pressed against the front part of the billet, the core may beprovided with at least one axial groove 21 through which air can flowfrom the front end of the billet to the aircollecting space.

FIG. 2 shows an embodiment of the billet in which the steel plate 15 isprovided with a bowl-shaped aircollecting space 22 and radial grooves 23through which the space 22 communicates with the triangular, annularspace 20. The bevelling 19 may be provided with slots 24 through whichair can flow to the slots 23 when the copper casing is forced into thespace 20.

We claim:

1. Method of manufacturing rods or wire of compound material having acore consisting essentially of aluminum and a casing consistingessentially of copper surrounding the core, by means of hydrostaticextrusion of a billet formed from a core and a casing wherein the casingis sealed at the rear end of the billet and surrounds the core, whichcomprises inserting said billet in a pressure chamber and forcing thebillet under the influence of a hydrostatic pressure through a die withan opening shaped to the desired cross-section, in which the billet isformed from a core having a smaller external diameter than the internaldiameter of the easing, thereby providing a clearance therebetween whichexceeds deformations normally occurring during annealing of the casingin which an internal space is provided at the rear of the billet tocollect in the gap between the core and the casing air which isdisplaced when the core and the casing are pressed into adhering contactwith each other.

2. Method according to claim 1, in which the normal radial clearancebetween the core and the casing exceeds 1 mm for a core diameter of mm.

3. Method according to claim 2, in which the nominal radial clearance isbetween 1 and 5 mm.

4. Method according to claim 1, in which the billet has a steel plate atthe rear end of the billet, the space for collecting the air being inthe vicinity of the steel plate.

5. Method according to claim 4, in which the steel plate has a partprojecting into the casing, said part being bevelled so that an annularspace is formed between the casing and the plate at the rear end surfaceof the core.

6. Method according to claim 5, in which the side of the plate facingthe end surface of the core is provided with a hollow therein.

7. Method according to claim 6, in which one of the end surfaces of theplate or the core is provided with radial grooves between the hollow andthe periphery.

8. Method accordinc to claim 1, in which the core or casing is providedwith at least one axial air-conducting groove therein.

2. Method according to claim 1, in which the normal radial clearancebetween the core and the casing exceeds 1 mm for a core diameter of100 - 150 mm.
 3. Method according to claim 2, in which the nominalradial clearance is between 1 and 5 mm.
 4. Method according to claim 1,in which the billet has a steel plate at the rear end of the billet, thespace for collecting the air being in the vicinity of the steel plate.5. Method according to claim 4, in which the steel plate has a partprojecting into the casing, said part being bevelled so that an annularspace is formed between the casing and the plate at the rear end surfaceof the core.
 6. Method according to claim 5, in which the side of theplate facing the end surface of the core is provided with a hollowtherein.
 7. Method according to claim 6, in which one of the endsurfaces of the plate or the core is provided with radial groovesbetween the hollow and the periphery.
 8. Method accordinc to claim 1, inwhich the core or casing is provided with at least one axialair-conducting groove therein.